Apparatus and method for injecting synchronized stream data in digital broadcasting environment

ABSTRACT

An apparatus and method for injecting synchronized stream data into a Motion Picture Experts Group 2 (MPEG-2) video/audio transport stream for a digital data broadcasting service. The apparatus and method for injecting synchronized stream data calculate the injection time point of data access unit (DAU) that forms the synchronized stream data and injects DAU into the MPEG-2 video/audio transport stream based on the calculated injection time point so that the synchronized stream data could be presented smoothly in a receiver. The synchronized stream data injecting apparatus includes: an additional data storing unit, a synchronized stream data selection/establishment unit, a synchronized stream data analyzing unit, a transport stream analyzing unit, a synchronized stream data injection/management unit, a presentation time stamp re-stamping unit and a multiplexing unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Reissue of application Ser. No. 10/693,130 filedon Oct. 23, 2003, now U.S. Pat. No. 7,406,703 issued on Jul. 29, 2008,and claims the benefit of Korean Patent Application No. 10-2002-0065642filed on Oct. 26, 2002, in the Korean Intellectual Property Office. Thedisclosures of application Ser. No. 10/693,130 and Korean PatentApplication No. 10-2002-0065642 are incorporated herein by reference intheir entirety.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for injectingsynchronized stream data into a Moving Picture Experts Group 2 (MPEG-2)video/audio transport stream (TS) for a digital data broadcastingservice.

DESCRIPTION OF RELATED ART

A digital broadcasting service has an advantage that diverse multimediadata could be transmitted along with video/audio data. The data that maybe provided in a digital broadcasting service includes asynchronousdata, synchronous data, synchronized data which are discriminated basedon the temporal relationship with video/audio data.

The asynchronous data are those that can be presented independentlyregardless of video/audio data. The asynchronous data may be used forproviding services, such as weather forecast, news, securities reportsand the like. In the meantime, most of the data broadcasting servicespractically used in Korea and other countries are asynchronous dataservices of a data carousel type. In data carousel type of data service,the asynchronous data is periodically injected into an MPEG-2video/audio transport stream and transmitted to a receiver. Thetransmitted data are executed in the receiver upon the request of auser.

Synchronous data use MPEG-2 program clock reference (PCR) and MPEG-2presentation time stamp (PTS) to temporally restrict the data presentedin the receiver.

Synchronized data are presented in connection with video/audio data.They use MPEG-2 PCR and MPEG-2 PTS to coincide the presentation timestamps of their data access units (DAU) and the access units (AUs) ofanother stream. Synchronized data have two types based on the continuityof data presentation: stream data and non-stream data.

First, synchronized non-stream data are those presented only once at aparticular time point of video/audio data. Information on a baseballplayer appearing at the bat, or information on a place shown up in aparticular scene of a soap opera should be presented only once inconnection with video data, it can be provided in the form ofsynchronized non-stream data.

Synchronized stream data are those data that should be presentedsuccessively in connection with video/audio data. MPEG video data orMPEG audio data may be used as synchronized stream. What can be providedin the synchronized stream data is past playing scenes or interviewscenes that are provided as moving picture when a particular playerappears in a sport game.

The synchronized data are presented in connection with other basicstream composing a video/audio program. So, they provide informationrelated to a particular scene. This is different from the services usingasynchronous data.

Technologies for providing synchronized data services are beingdeveloped in the inside and outside of the country. Among them, DataInterface Working Group (DIWG), which is an embodiment work group ofAdvanced Television System Committee (ATSC), is a representative one.

DIWG has presented a system model formed of various functional modulesto embody a synchronized data broadcasting system. However, since thesystem model includes a function that a module encoding video/audio datainto an MPEG-2 transport stream multiplexes additional datasimultaneously, it has a problem that it is not compatible withconventional digital broadcasting apparatuses which multiplexvideo/audio data only.

In addition, since the system suggested by DIWG is for synchronizednon-stream data, it has another problem that it could not provide aservice of synchronized stream data.

Meanwhile, the synchronized data are presented at a moment presentationtime stamp of the synchronized data is coincided with the reference timeof the receiver, which is a system time clock (STC). Synchronizednon-stream data are presented only once at a particular time point. So,if the synchronized non-stream data arrives in the receiver before thevalue of STC becomes equal to the presentation time stamp of thesynchronized non-stream data, the data may be presented in the receiverwithout any problem. The synchronized stream data includes successiveDAU and each DAU has its own presentation time stamp. Buffer models forthe synchronized stream data are defined for the receiver to present theDAU successively and smoothly. However, the defined receiver buffermodels may cause buffer overflow due to the other DAU existing in thebuffer, when the DAU arrives in the receiver too quickly, and thusbrings about data loss. Therefore, the synchronized stream data shouldbe outputted in consideration of whether DAU has arrived in thereceiver.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide anapparatus and method for injecting synchronized stream data for adigital data broadcasting service, the apparatus and method calculatingan injection time point with respect to each data access unit (DAU)which forms synchronized stream data so that the synchronized streamdata could be presented in a receiver smoothly, and injecting the DAUinto a Moving Picture Experts Group 2 (MPEG-2) audio/video transportstream at the calculated injection time point.

In accordance with an aspect of the present invention, there is providedan apparatus for injecting synchronized stream data for a digital databroadcasting service, including: an additional data storing unit forstoring, managing and outputting additional data used for the digitaldata broadcasting service; a synchronized stream dataselection/establishment unit for selecting synchronized stream data tobe multiplexed with a video/audio transport stream, which is inputtedfrom the outside, among the additional data stored in the additionaldata storing unit, and establishing parameter values necessary tomultiplex the selected synchronized stream data and the video/audiotransport stream; a synchronized stream data analyzing unit foranalyzing the selected synchronized stream data periodically based onthe parameter values established in the synchronized stream dataselection/establishment unit, and generating information related to thetransport stream of the synchronized stream data; a transport streamanalyzing unit for analyzing the video/audio transport streamperiodically based on the parameter values established in thesynchronized stream data selection/establishment unit, and generatinginformation related to the video/audio transport stream; a synchronizedstream data injection/management unit for determining whether to injecta data access unit (DAU) that forms the synchronized stream data or notbased on the information related to the synchronized stream datatransport stream generated in the synchronized stream data analyzingunit and the information related to the video/audio transport streamgenerated in the transport stream analyzing unit, and controlling theoutput of the DAU that forms the synchronized stream data which arestored in the additional data storing unit; a presentation time stampre-stamping unit for re-stamping the presentation time stamp of thesynchronized stream data which are outputted from the additional datastoring unit based on the parameter values established in thesynchronized stream data selection/establishment unit; and amultiplexing unit for multiplexing and outputting the video/audiotransport stream and the synchronized data outputted from thepresentation time stamp re-stamping unit.

In accordance with another aspect of the present invention, there isprovided a method for injecting synchronized stream data for a digitaldata broadcasting service, including the steps of: a) selectingsynchronized stream data that are synchronized with a video/audiotransport stream supplied from the outside among additional data usedfor the digital data broadcasting service, and establishing an injectionperiod which is a time interval for analyzing the video/audio transportstream and the synchronized stream data and injecting the synchronizedstream data, the number of analyzed DAU which is the largest number ofDAU that can be injected into the video/audio transport stream duringthe above established injection period, and a new presentation timestamp of a first data access unit (DAU) of the synchronized stream data;b) obtaining the presentation time stamp of a corresponding DAU and thenumber of transport stream packets by analyzing the selectedsynchronized stream data periodically based on the injection period andthe number of analyzed DAU which are established in the step a), andobtaining as many DAU as the analyzed DAU; c) obtaining PCR informationof the video/audio transport stream within the analyzing section byanalyzing the video/audio transport stream periodically based on theinjection period determined in the step a); d) determining whether toinject the DAU of the synchronized stream data into the video/audiotransport stream within the analyzing section or not based on the newpresentation time stamp of the first DAU of the synchronized streamdata, presentation time stamp of DAU of the synchronized stream data andthe PCR information of the video/audio transport stream; e) if the DAUof the synchronized stream data is to be injected into the video/audiotransport stream within the analyzing section, re-stamping thepresentation time stamp of DAU of the synchronized stream data by usingthe new presentation time stamp of the first DAU of the synchronizedstream data; and f) injecting the DAU of the synchronized stream datawhose presentation time stamp is re-stamped newly into the video/audiotransport stream and outputting the video/audio transport stream withthe DAU.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of the preferredembodiments given in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a block diagram illustrating a digital data broadcastingsystem to which the technology of the present invention is applied;

FIG. 2 is a block diagram describing a synchronized data injecting block400 in accordance with an embodiment of the present invention;

FIG. 3 is a flow chart describing a synchronized stream data injectingprocess of the synchronized data injecting block 400 in accordance withan embodiment of the present invention; and

FIG. 4 is a flow chart further describing a process for re-stamping thepresentation time stamp of additional data in the synchronized streamdata injecting process in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Other objects and aspects of the invention will become apparent from thefollowing description of the embodiments with reference to theaccompanying drawings, which is set forth hereinafter.

FIG. 1 is a block diagram illustrating a digital data broadcastingsystem to which the technology of the present invention is applied. Asshown in the drawing, the digital data broadcasting system, to which thepresent invention is applied, includes: a video/audio storage 100, avideo/audio encoding block 200, a program multiplexing block (PMUX) 300,a synchronized stream data injecting block 400, a Program and SystemInformation Protocol (PSIP)/Service Information (SI) generating block500 and a re-multiplexing block 600.

The video/audio storage 100 stores and manages a predetermined size ofvideo/audio data transmitted from the outside.

The video/audio encoding block 200 performs encoding of the video/audiodata transmitted from the video/audio storage 100 based on MovingPicture Experts Group 2 (MPEG-2) standards.

The program multiplexing block (PMUX) 300 packetizes the MPEG-2video/audio elementary stream (ES) transmitted from the video/audioencoding block 200 into a packetized elementary stream (PES). The PMUX300 also generates program specific information (PSI) or serviceinformation (SI) of the PES and converts them into transport streampackets.

The synchronized stream data injecting block 400 selects synchronizedstream data, which are synchronized with the MPEG-2 video/audiotransport stream, among the additional data in the synchronized streamdata injecting block 400, and injects the synchronized stream data intothe video/audio transport stream and outputs it.

The PSIP/SI generating block 500 generates, manages and outputs programguidance information (PSIP table or SI table) of an Advanced TelevisionSystems Committee (ATSC) standards or Digital Video Broadcasting (DVB)standards in order to guide the programs of a digital data broadcastingservice.

The re-multiplexing block 600 abstracts and re-constructs PSIP/SI/PSI ofseveral transport streams, which are transmitted from the synchronizedstream data injecting block 400 and PSIP/SI generating block 500. Ifnecessary, it can give a packet identifier (PID). In addition, it canoutput a corresponding transport stream by adjusting program clockreference (PCR).

Referring to FIG. 2, the structure of the synchronized stream datainjecting block 400 of the present invention will be described herein ina digital broadcasting system having the above-described structure.

FIG. 2 is a block diagram describing a synchronized data injecting block400 in accordance with an embodiment of the present invention. Asillustrated in the drawing, the synchronized data injecting block 400 ofthe present invention includes: an additional data storing unit 440, asynchronized stream data selection/establishment unit 410, asynchronized stream data injection/management unit 420, a synchronizedstream data analyzing unit 430, a transport stream analyzing unit 450, apresentation time stamp re-stamping unit 460 and a multiplexing unit470.

The additional data storing unit 440 stores, manages and outputsadditional data including the synchronized stream data which isencapsulated in the form of an MPEG-2 transport stream that are used ina digital data broadcasting service. Here, the output time point of thesynchronized stream data which are stored in the additional data storingunit 440 is determined based on a control signal transmitted from thesynchronized stream data injection/management unit 420.

The synchronized stream data selection/establishment unit 410 selectssynchronized stream data which are synchronized with a video/audiotransport stream inputted from the outside among the additional datastored in the additional data storing unit 440. Also, the synchronizedstream data selection/establishment unit 410 establishes the values ofparameters, such as an injection period, which is time interval forinjecting synchronized stream data into a video/audio transport stream,a new presentation time stamp of a first DAU of the selectedsynchronized stream data, and the number of analyzed DAU, which meansthe maximum number of DAU of synchronized stream data that can beinjected in one injection period. The synchronized stream data analyzingunit 430 obtains as many DAU as the number of analyzed DAU by analyzingthe synchronized stream data selected based on the injection period andthe number of analyzed DAU that are established in the additional dataselection/establishment unit 410, and generates information related tothe synchronized stream data, such as the presentation time stamp of acorresponding DAU, and the number of transport stream packets.

The transport stream analyzing unit 450 analyzes video/audio transportstream periodically based on the injection period established in theadditional data selection/establishment unit 410, and generatesinformation related to the video/audio transport stream, such as PCR ofvideo/audio transport stream. Here, the PCR value of transport streamcan be obtained directly from a transport stream including PCR withinthe analysis section, and PCR for another transport stream packet iscalculated based on the output rate of MPEG-2 transport stream.Otherwise, PCR values can be obtained by putting a reference clock thatincreases at 27 MHz which is the same as the per-second increase of PCRin the transport stream analyzing unit 450, obtaining PCR from atransport stream packet including PCR among the inputted MPEG2 transportstreams, establishing as the reference clock the same value as theobtained PCR, and obtaining the value of the reference clock at anecessary moment.

The synchronized stream data injection/management unit 420 calculatesthe presentation time offset value by using the difference between thenew presentation time stamp of a first DAU of the synchronized streamdata and the presentation time stamp of a first DAU of the synchronizedstream data obtained in the synchronized stream data analyzing unit 430,calculates a new presentation time stamp of DAU of the synchronizedstream data by adding the presentation time offset value to thepresentation time stamp of DAU of the synchronized stream data obtainedin the synchronized stream data analyzing unit 430, and compares it withthe PCR, which is generated periodically based on the injection periodsestablished in the additional data selection/establishment unit 410, inthe transport stream analyzing unit 450. If the new presentation timestamp of DAU is larger than PCR_base of the final part of thevideo/audio transport stream currently analyzed and smaller than a valueobtained by adding the increase of PCR_base that increases during aperiod to PCR_base of the final part, it is determined as a time pointfor injecting DAU and a corresponding DAU is controlled to be outputtedfrom the additional data storing unit 440.

Here, the increase of PCR_base increasing for one period can becalculated as shown in FIG. 1 by using the per-second increase ofPCR_base, i.e., 90,000, and the injection period established in theadditional data selection/establishment unit 410.PCR_base increase during a period=injection period×90,000  Eq. 1

When a new presentation time stamp is stamped for the synchronizedstream data in the synchronized stream data selection/establishment unit410, the presentation time stamp re-stamping unit 460 re-stamps thepresentation time stamp of the synchronized stream data into the newpresentation time stamp.

The multiplexing unit 470 injects DAU of the synchronized stream data,which are outputted from the presentation time stamp re-stamping unit460, into the video/audio transport stream outputted from the transportstream analyzing unit 450.

Referring to FIG. 3, the operation of the synchronized stream datainjecting block 400 having the above-described structure will bedescribed hereinafter.

FIG. 3 is a flow chart describing a synchronized stream data injectingprocess of the synchronized stream data injecting block 400 inaccordance with an embodiment of the present invention. As illustratedin the drawing, at step S310, the synchronized stream dataselection/establishment unit 410 of the synchronized stream datainjecting block 400 selects synchronized stream data that aresynchronized with the video/audio transport stream inputted from theoutside among the additional data stored in the additional data storingunit 440.

Also, it establishes the values of parameters, such as an injectionperiod, which is time interval for injecting synchronized stream datainto a video/audio transport stream, a new presentation time stamp of afirst DAU of the above-selected synchronized stream data, and the numberof analyzed DAU, which means the maximum number of DAU of synchronizedstream data that can be injected in one injection period. Here, if thenumber of analyzed DAU is not established, it is calculated bymultiplying the largest value (59.94 or 60) of the number of frequencyof DAU generation to the established injection period. If both injectionperiod and the number of analyzed DAU are not established, the injectionperiod is set to be 50 msec and the number of analyzed DAU is determinedto be 3.

Subsequently, at step S320, the synchronized stream data analyzing unit430 analyzes the synchronized stream data selected in the additionaldata selection/establishment unit 410 based on the injection period andthe number of analyzed DAU, which are established in the additional dataselection/establishment unit 410, periodically to obtain as many DAU asthe number of analyzed DAU, and generates information related tosynchronized stream data, such as presentation time stamp of acorresponding DAU, the number transport stream packets.

Subsequently, at step S330, the transport stream analyzing unit 450periodically analyzes the video/audio transport stream inputted from theoutside in real-time based on the injection period established in theadditional data selection/establishment unit 410, and generatesinformation needed to inject the synchronized stream data, such as PCRof the video/audio transport stream within the analysis section.

Subsequently, at step S340, it is determined whether it is a section forinjecting DAUs of a synchronized stream data. The synchronized streamdata injection/management unit 420 calculates a presentation time offsetby using the difference between a new presentation time stamp of a firstDAU of the synchronized stream data established in the additional dataselection/establishment unit 410 and the presentation time stamp of afirst DAU of the synchronized stream data obtained in the synchronizedstream data analyzing unit 430.

Then, the synchronized stream data injection/management unit 420calculates a new presentation time stamp of DAU of the synchronizedstream data obtained in the synchronized stream data analyzing unit 430.It determines whether to inject DAU of the synchronized stream data intothe video/audio transport stream within the analysis section bycomparing the new presentation time stamp calculated above with PCRobtained from the analysis of the video/audio transport stream. If theDAU of the synchronized stream data is determined for injection,synchronized stream data injection/management unit 420 controls theadditional data storing unit 440 to output corresponding DAU.

Subsequently, at step S350, if a new presentation time stamp isestablished with respect to a first DAU of synchronized stream data inthe synchronized stream data selection/establishment unit 410, thepresentation time stamp re-stamping unit 460 re-stamps the presentationtime stamp of DAU that forms synchronized stream data outputted from theadditional data storing unit 440 based on the control of thesynchronized stream data injection/management unit 420, by referring tothe presentation time stamp newly stamped in the synchronized streamdata selection/establishment unit 410. If the DAU of the synchronizedstream data is not injected, process goes back to the step S320.

Here, to re-stamp the presentation time stamp of all DAU that formsynchronized stream data, a presentation time offset value is calculatedby using the difference between the presentation time stamp of the firstDAU of the synchronized stream data and the new presentation time stampstamped in the synchronized stream data selection/establishment unit410. Here, the summation of the presentation time stamp of the first DAUof the synchronized stream data and the calculated presentation timeoffset value should be equal to the new presentation time stamp.

The presentation time stamp of all DAU that forms the synchronizedstream data is re-stamped by adding the presentation time offset valueto the presentation time stamp of all DAU of the synchronized streamdata.

Subsequently, at step S360, the multiplexing unit 470 injects the DAU ofthe synchronized stream data outputted from the presentation time stampre-stamping unit 460 into the video/audio transport stream outputtedfrom the transport stream analyzing unit 450 and outputs one transportstream.

At step 370, it is determined whether all of DAUs are injected or not.If all of DAUs are not injected, i.e., is there any DAU to be injected,process continues to the step S320.

FIG. 4 is a flow chart further describing a process (S350) forre-stamping the presentation time stamp of additional data in thesynchronized stream data injecting process in accordance with anembodiment of the present invention.

First, to re-stamp the presentation time stamp of DAU that formssynchronized stream data, at step S351, it is checked if a newpresentation time stamp of a first DAU of synchronized stream data isstamped through the synchronized stream data selection/establishmentunit 410.

If a new presentation time stamp of the first DAU of the synchronizedstream data is not stamped, the presentation time stamp re-stampingprocess is terminated, and if a new presentation time stamp is stamped,at step S352, the presentation time offset value is calculated. Thepresentation time offset value of the synchronized stream data can beobtained by subtracting the actual presentation time stamp the first DAUof the synchronized stream data from the newly stamped presentation timestamp of the first DAU of the synchronized stream data, as shown inbelow Equation 2.

$\begin{matrix}{{{presentation}\mspace{14mu}{time}\mspace{14mu}{offset}\mspace{14mu}\left( {PTS}_{off} \right)} = {{{new}\mspace{14mu}{presentation}\mspace{14mu}{time}\mspace{14mu}{stamp}} - {{presentation}\mspace{14mu}{time}\mspace{14mu}{stamp}\mspace{14mu}{of}\mspace{14mu} a\mspace{14mu}{first}\mspace{14mu}{DAU}}}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

When the presentation time offset of the synchronized stream data iscalculated, at step S353, the re-stamped presentation time stamp of eachDAU that forms the synchronized stream data is calculated andre-stamped. The re-stamped presentation time stamp of DAU that formssynchronized stream data can be calculated by adding the presentationtime offset to the presentation time stamp of all DAU that form thesynchronized stream data, as shown in Equation 3.Re-stamped presentation time stamp of DAU=Presentation time stamp of aDAU+PTS_(off)   Eq. 3

As described above, the present invention discloses an apparatus forinjecting synchronized stream data, which is a stream data synchronizedwith audio/video data temporally, into an MPEG-2 video/audio transportstream. This technology can be used to establish a digital databroadcasting system that can provide a synchronized stream data service,which is capable of providing more diverse data service to viewers.

While the present invention has been described with respect to certainpreferred embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the scope of the invention as defined in the following claims.

What is claimed is:
 1. An apparatus for injecting synchronized streamdata for a digital data broadcasting service, comprising: an additionaldata storing means for storing, managing and outputting additional dataused for the digital data broadcasting service; a synchronized streamdata selection/establishment means for selecting synchronized streamdata to be multiplexed with a video/audio transport stream, which isinputted from the outside, among the additional data stored in theadditional data storing means, and establishing parameter valuesnecessary to multiplex the selected synchronized stream data and thevideo/audio transport stream; a synchronized stream data analyzing meansfor analyzing the selected synchronized stream data periodically basedon the parameter values established in the synchronized stream dataselection/establishment means, and generating information related to thetransport stream of the synchronized stream data; a transport streamanalyzing means for analyzing the video/audio transport streamperiodically based on the parameter values established in thesynchronized stream data selection/establishment means, and generatinginformation related to the video/audio transport stream; a synchronizedstream data injection/management means for determining whether to injecta data access unit (DAU) that forms the synchronized stream data or notbased on the information related to the synchronized stream datatransport stream generated in the synchronized stream data analyzingmeans and the information related to the video/audio transport streamgenerated in the transport stream analyzing means, and controlling theoutput of the DAU that forms the synchronized stream data which arestored in the additional data storing means; a presentation time stampre-stamping means for re-stamping the presentation time stamp of thesynchronized stream data which are outputted from the additional datastoring means based on the parameter values established in thesynchronized stream data selection/establishment means; and amultiplexing means for multiplexing and outputting the video/audiotransport stream and the synchronized stream data outputted from thepresentation time stamp re-stamping means.
 2. The apparatus as recitedin claim 1, wherein the parameter values established in the synchronizedstream data selection/establishment means include at least any oneselected from a group having a new presentation time stamp of a firstDAU of the synchronized stream data; an injection period, which is atime interval for analyzing the video/audio transport stream andsynchronized stream data and injecting the synchronized stream data tothe video/audio transport stream; and the number of analyzed DAUs withinthe analyzed synchronized stream data during the above establishedinjection period.
 3. The apparatus as recited in claim 1, wherein if thenumber of analyzed DAUs is not established in the synchronized streamdata selection/establishment means, the synchronized stream dataselection/establishment means calculates the number of analyzed DAUs bymultiplying the largest value (59.94 or 60) of the number of frequencyof DAU generation to the established injection period, and if theinjection period and the number of analyzed DAUs are not established inthe synchronized stream data selection/establishment means, theinjection period and the number of DAU to be injected are determined tobe 50 msec and 3, respectively.
 4. The apparatus as recited in claim 1,wherein if synchronized stream data synchronized with the video/audiotransport stream are not stored in the additional data storing means,the synchronized stream data selection/establishment means receives thesynchronized stream data from the outside and stores the synchronizedstream data in the additional data storing means.
 5. The apparatus asrecited in claim 1, wherein the synchronized stream data analyzing meansobtains many as DAUs as the analyzed DAU by analyzing the synchronizedstream data selected in the synchronized stream dataselection/establishment means based on an injection period and thenumber of analyzed DAUs established in the synchronized stream dataselection/establishment means, and obtains the presentation time stampof a corresponding DAU and the number of transport stream packets. 6.The apparatus as recited in claim 1, wherein the transport streamanalyzing means analyzes the video/audio transport stream periodicallybased on an injection period established in the synchronized stream dataselection/establishment means, and obtains the program clock references(PCRs) of a beginning part and a final part of an analyzing section ofthe video/audio transport stream analyzed during one injection period.7. The apparatus as recited in claim 1, wherein in order to calculatePCR of the transport stream, the transport stream analyzing meansdirectly obtains a PCR value from a transport stream including PCRwithin an analyzing section, obtains PCR from the transport streampackets including PCR among an inputted MPEG-2 transport streams bycalculating the PCR for another transport stream packet using an outputrate of the MPEG-2 transport stream, or by having a reference clock thatincreases at 27 MHz which is a per-second increase of PCR of thetransport stream analyzing means, and obtains the PCR value byestablishing the value of the reference clock with the same value as theobtained PCR and then obtaining the value of the reference clock at amoment when the PCR value is needed.
 8. The apparatus as recited inclaim 1, wherein the synchronized stream data injection/management meanscalculates the presentation time offset value by using the differencebetween the new presentation time stamp of a first DAU of thesynchronized stream data established in the synchronized stream dataselection/establishment means and the presentation time stamp of thefirst DAU of the synchronized stream data obtained in the synchronizedstream data analyzing means, calculates a new presentation time stamp ofDAU of the synchronized stream data by adding the presentation timeoffset value to the presentation time stamp of DAU of the synchronizedstream data obtained periodically in the synchronized stream dataanalyzing means, compares the calculated new presentation time stampwith the PCR generated periodically based on an injection period, whichis established in the synchronized stream data selection/establishmentmeans, in the transport stream analyzing means, and if the newpresentation time stamp of DAU is larger than the PCR in the final partof the video/audio transport stream currently analyzed and smaller thanthe summation of the PCR increase during one period and the PCR of thefinal part, determines to inject the corresponding DAU, and controls theadditional data storing means to output the corresponding DAU.
 9. Theapparatus as recited in claim 1, wherein if a new presentation timestamp for an first DAU is stamped in the synchronized stream dataselection/establishment means, the presentation time stamp re-stampingmeans receives synchronized stream data outputted from the additionaldata storing means, re-stamps the presentation time stamp of a DAU thatforms the synchronized stream data by referring to the presentation timestamp newly stamped in the synchronized stream dataselection/establishment means, and outputs the re-stamped presentationtime stamp of the DAU to the multiplexing means, and wherein, tore-stamp the presentation time stamp of all DAUs that form thesynchronized stream data, the presentation time stamp re-stamping meanscalculates a presentation time offset value by using the differencebetween the presentation time stamp of the first DAU of the synchronizedstream data and the new presentation time stamp stamped in thesynchronized stream data selection/establishment means, and re-stampsthe presentation time stamp of all DAUs that form the synchronizedstream data by adding the presentation time offset value to thepresentation time stamp of all DAUs that form the synchronized streamdata.
 10. The apparatus as recited in claim 1, wherein the multiplexingmeans injects the DAU of the synchronized stream data outputted from thepresentation time stamp re-staming means into the places of null packetsin the video/audio transport stream within a section analyzed in thetransport stream analyzing means, instead of the null packets.
 11. Theapparatus as recited in claim 1, wherein if the number of DAUsmultiplexed in the video/audio transport stream analyzed in thetransport stream analyzing means is more than two, the multiplexingmeans injects the DAUs into the video/audio transport stream in theorder of quick presentation time stamp, and the locations for DAU to beinjected into are moved from a part where PCR of the analyzedvideo/audio transport stream is small to a part where PCR of theanalyzed video/audio transport stream is large.
 12. A method forinjecting synchronized stream data for a digital data broadcastingservice, comprising the steps of: a) selecting synchronized stream datathat are synchronized with a video/audio transport stream supplied fromthe outside among additional data used for the digital data broadcastingservice, and establishing an injection period which is a time intervalfor analyzing the video/audio transport stream and the synchronizedstream data and injecting the synchronized stream data, the number ofanalyzed DAUs which is the largest number of DAUs that can be injectedinto the video/audio transport stream during the above establishedinjection period, and a new presentation time stamp of a first dataaccess unit (DAU) of the synchronized stream data; b) obtaining thepresentation time stamp of a corresponding DAU and the number oftransport stream packets by analyzing the selected synchronized streamdata periodically based on the injection period and the number ofanalyzed DAU which are established in the step a), and obtaining as manyas DAUs as the analyzed DAUs; c) obtaining PCR information of thevideo/audio transport stream within an analyzing section by analyzingthe video/audio transport stream periodically based on the injectionperiod determined in the step a); d) determining whether to inject theDAU of the synchronized stream data into the video/audio transportstream within the analyzing section or not based on the new presentationtime stamp of the first DAU of the synchronized stream data,presentation time stamp of DAU of the synchronized stream data and thePCR information of the video/audio transport stream; e) if the DAU ofthe synchronized stream data is to be injected into the video/audiotransport stream within the analyzing section, re-stamping thepresentation time stamp of DAU of the synchronized stream data by usingthe new presentation time stamp of the first DAU of the synchronizedstream data; and f) injecting the DAU of the synchronized stream datawhose presentation time stamp is re-stamped newly into the video/audiotransport stream and outputting the video/audio transport stream withthe DAU.
 13. The method as recited in claim 12, further comprising thestep of: g) going back to the step b) if the analyzing section does notsatisfy the condition for injecting the DAU.
 14. The method as recitedin claim 12, further comprising the step of: h) determining whether allof the DAUs of synchronized stream data are injected or not, and goingback to the step b) if there remain any of the DAUs to be injected,otherwise, ending the method.
 15. The method as recited in claim 12,wherein the step a) includes the steps of: a1) if the number of analyzedDAU is not established, calculating the number of analyzed DAU bymultiplying the largest value (59.94 or 60) of the number of frequencyof DAU generation to the injection period established above; and a2) ifthe injection period and the number of analyzed DAU are not established,determining the injection period and the number of analyzed DAU to be 50msec and 3, respectively.
 16. The method as recited in claim 12, whereinthe PCRs of the beginning part and the final part of the analyzingsection of the video/audio transport stream analyzed during oneinjection period are obtained by analyzing the video/audio transportstream periodically based on the injection period.
 17. The method asrecited in claim 12, wherein said step d) includes the steps of: d1)calculating a new presentation time stamp one of the DAUs based on thenew presentation time stamp of a first DAU of the synchronized streamdata established in the step a) and the presentation time stamp of DAUof the synchronized stream data which are obtained periodically at thestep b); d2) comparing the new presentation time stamp of the DAU withthe PCR information of the video/audio transport stream obtained in thestep c); d3) if the new substantial presentation time stamp of the DAUis larger than a base value PCR_base of the PCR of the video/audiotransport stream and smaller than a summation value of increase of thebase value PCR_base during one injection period and the base valuePCR_base of the PCR of the video/audio transport stream, deciding a timeto inject the DAU of the synchronized stream data into the video/audiotransport stream.
 18. The method as recited in claim 17, wherein thestep d1) includes the steps of: d1-1) calculating a presentation timeoffset value by using the difference between the new presentation timestamp of the first DAU of the synchronized stream data established inthe step a) and the presentation time stamp of the first DAU of thesynchronized stream data obtained in the step b); and d1-2) calculatingthe new presentation time stamp of the DAU of the synchronized streamdata by adding the presentation time offset value to the presentationtime stamp of DAU of the synchronized stream data.
 19. The method asrecited in claim 12, wherein the step e) includes the steps of: e1)checking if a new presentation time stamp for the first DAU of theselected synchronized stream data is established; e2) if a newpresentation time stamp for the first DAU of the selected synchronizedstream data is established, calculating a presentation time offset valueby subtracting the presentation time stamp of the first DAU of theactual synchronized stream data from the new presentation time stamp, orotherwise, terminating the process of re-stamping the presentation timestamp; and e3) adding the calculated presentation time offset value tothe actual presentation time stamp of all DAUs of the inputtedsynchronized stream data.
 20. The method as recited in claim 19, whereinthe step e) further includes the step of: if a new presentation timestamp for the first DAU of the selected synchronized stream data is notestablished, returning to the step f).
 21. An apparatus for injectingsynchronized stream data for a digital data broadcasting service,comprising: an additional data storing unit that stores, manages, andoutputs additional data used for the digital data broadcasting service;a synchronized stream data selection/establishment unit that selectssynchronized stream data to be multiplexed with a video/audio transportstream, which is inputted from the outside, among the additional datastored in the additional data storing unit, and establishes parametervalues necessary to multiplex the selected synchronized stream data andthe video/audio transport stream; a synchronized stream data analyzingunit that analyzes the selected synchronized stream data periodicallybased on the parameter values established in the synchronized streamdata selection/establishment unit, and generates information related tothe transport stream of the synchronized stream data; a transport streamanalyzing unit that analyzes the video/audio transport streamperiodically, and generates information related to the video/audiotransport stream; a synchronized stream data injection/management unitthat determines whether to inject a data access unit (DAU) that formsthe synchronized stream data or not based on the information related tothe synchronized stream data transport stream generated in thesynchronized stream data analyzing unit and the information related tothe video/audio transport stream generated in the transport streamanalyzing unit, and controls the output of the DAU that forms thesynchronized stream data which are stored in the additional data storingunit; a presentation time stamp re-stamping unit that re-stamps thepresentation time stamp of the synchronized stream data which areoutputted from the additional data storing unit based on the parametervalues established in the synchronized stream dataselection/establishment unit; and a multiplexing unit that multiplexesand outputs the video/audio transport stream and the synchronized streamdata outputted from the presentation time stamp re-stamping unit.
 22. Amethod for injecting synchronized stream data for a digital databroadcasting service, comprising the steps of: a) selecting synchronizedstream data that are synchronized with a video/audio transport streamsupplied from the outside among additional data used for the digitaldata broadcasting service, and establishing an injection period which isa time interval for analyzing the video/audio transport stream and thesynchronized stream data and injecting the synchronized stream data, thenumber of analyzed DAUs which is the largest number of DAUs that can beinjected into the video/audio transport stream during the aboveestablished injection period, and a new presentation time stamp of afirst data access unit (DAU) of the synchronized stream data; b)obtaining the presentation time stamp of a corresponding DAU and thenumber of transport stream packets by analyzing the selectedsynchronized stream data periodically based on the injection period andthe number of analyzed DAU which are established in the step a), andobtaining as many as DAUs as the analyzed DAUs; c) obtaining PCRinformation of the video/audio transport stream within an analyzingsection by analyzing the video/audio transport stream periodically; d)determining whether to inject the DAU of the synchronized stream datainto the video/audio transport stream within the analyzing section ornot based on the new presentation time stamp of the first DAU of thesynchronized stream data, presentation time stamp of DAU of thesynchronized stream data and the PCR information of the video/audiotransport stream; e) if the DAU of the synchronized stream data is to beinjected into the video/audio transport stream within the analyzingsection, re-stamping the presentation time stamp of DAU of thesynchronized stream data by using the new presentation time stamp of thefirst DAU of the synchronized stream data; and f) injecting the DAU ofthe synchronized stream data whose presentation time stamp is re-stampednewly into the video/audio transport stream and outputting thevideo/audio transport stream with the DAU.
 23. An apparatus configuredto inject synchronized stream data into a transport stream, theapparatus comprising: a data storing unit configured to storesynchronized stream data; a synchronized stream dataselection/establishment unit configured to select synchronized streamdata corresponding to the transport stream; a synchronized stream dataanalyzing unit configured to analyze the selected synchronized streamdata and generate information related to the synchronized stream data; atransport stream analyzing unit configured to analyze the transportstream and generate information related to the transport stream; asynchronized stream data injection/management unit configured todetermine whether to inject the selected synchronized stream data basedon the information related to the synchronized stream data and theinformation related to the transport stream, and control the datastoring unit to output the corresponding synchronized stream data basedon the determination; a presentation time stamp re-stamping unitconfigured to re-stamp the synchronized stream data outputted from thedata storing unit with a new presentation time stamp; and a multiplexingunit configured to multiplex the transport stream and the synchronizedstream data.
 24. The apparatus as recited in claim 23, wherein thesynchronized stream data is encapsulated in a MPEG-2 transport streamform.
 25. The apparatus as recited in claim 23, wherein if theadditional data storing unit does not store the synchronized stream datacorresponding to the transport stream, the synchronized stream dataselection/establishment unit is further configured to receive thesynchronized stream data from outside and store the receivedsynchronized stream data in the data storing unit.
 26. The apparatus asrecited in claim 23, wherein the synchronized stream dataselection/establishment unit is further configured to establishparameter values.
 27. The apparatus as recited in claim 26, wherein theparameter values comprise: a new presentation time stamp of a first dataaccess unit (DAU) of the selected synchronized stream data: an injectionperiod, wherein the injection period is a time interval for injectingthe synchronized stream data into the transport stream; and a maximumnumber of DAUs of the synchronized stream data that can be injected inone injection period.
 28. The apparatus as recited in claim 27, whereinthe synchronized stream data analyzing unit is further configured toobtain as many DAUs as the maximum number of the DAUs by analyzing theselected synchronized stream data based on the parameter values.
 29. Theapparatus as recited in claim 27, wherein the transport stream analyzingunit is further configured to periodically analyze the transport streambased on the parameter values.
 30. The apparatus as recited in claim 23,wherein the information related to the synchronized stream datacomprises: a presentation time stamp of a corresponding DAU; and anumber of transport stream packets.
 31. The apparatus as recited inclaim 30, wherein the synchronized stream data injection/management unitis further configured to calculate a presentation time offset by using adifference between the new presentation time stamp of a first dataaccess unit (DAU) of the selected synchronized stream data and apresentation time stamp of a corresponding DAU generated from thesynchronized stream data analyzing unit.
 32. The apparatus as recited inclaim 31, wherein the synchronized stream data injection/management unitis further configured to calculate a new presentation time stamp of DAUof the synchronized stream data by adding the presentation time offsetto the presentation time stamp of a corresponding DAU.
 33. The apparatusas recited in claim 32, wherein the synchronized stream datainjection/management unit is further configured to compare the newpresentation time stamp of DAU with the presentation time stamp of acorresponding DAU generated in the transport analyzing unit.
 34. Theapparatus as recited in claim 33, wherein if the new presentation timestamp of DAU is larger than the PCR in the final part of the video/audiotransport stream currently analyzed and smaller than the summation ofthe PCR increase during one period and the PCR of the final part, thesynchronized stream data injection/management unit is further configuredto determine to inject the corresponding DAU, and control the datastoring unit to output the corresponding DAU.
 35. The apparatus asrecited in claim 23, wherein the information related to the transportstream is a program clock reference (PCR) of the transport stream. 36.The apparatus as recited in claim 35, wherein the transport streamanalyzing unit is further configured to obtain the PCR directly from thetransport stream including PCR within an analyzing section, andcalculate PCR for another transport stream packet based on an outputrate of the transport stream.
 37. The apparatus as recited in claim 35,wherein the transport stream analyzing unit is further configured toobtain the PCR by putting a reference clock that increases as 27 MHz,wherein the 27 MHz is a per-second increase of PCR of the transportstream analyzing unit.
 38. The apparatus as recited in claim 35, whereinthe transport stream analyzing unit is further configured to obtain thePCR by establishing a value of the reference clock with the same valueas the obtained PCR and obtain the value of the reference clock at amoment when the PCR value is needed.
 39. The apparatus as recited inclaim 23, wherein if a new presentation time stamp for a first DAU isstamped in the synchronized stream data selection/establishment unit,the presentation time stamp re-stamping unit is further configured to:receive the synchronized stream data outputted from the data storingunit; re-stamp the presentation time stamp of a DAU by referring to thepresentation time stamp newly stamped in the synchronized stream dataselection/establishment unit; and output the re-stamped presentationtime stamp of the DAU to the multiplexing unit.
 40. The apparatus asrecited in claim 39, wherein the presentation time stamp re-stampingunit is further configured to: calculate a presentation time offsetvalue by using the difference between the presentation time stamp of thefirst DAU of the synchronized stream data and the new presentation timestamp stamped in the synchronized stream data selection/establishmentunit; and re-stamp the presentation time stamp of all DAUs by adding thepresentation time offset value to the presentation time stamp of allDAUs.
 41. The apparatus as recited in claim 23, wherein the multiplexingunit is further configured to inject DAUs of the synchronized streamdata outputted from the presentation time stamp re-stamping unit intothe places of null packets in the transport stream within a sectionanalyzed in the transport stream analyzing unit, instead of the nullpackets.
 42. The apparatus as recited in claim 23, wherein if a numberof DAUs of the synchronized stream data multiplexed in the transportstream analyzed in the transport stream analyzing unit is more than two,the multiplexing unit is further configured to inject the DAUs into thetransport stream in the order of quick presentation time stamp, and thelocations for DAU to be injected into are moved from a part where PCR ofthe analyzed transport stream is small to a part where PCR of theanalyzed transport stream is large.
 43. A method for injectingsynchronized stream data into a transport stream, the method comprising:selecting synchronized stream data corresponding to the transportstream; analyzing the selected synchronized stream data and generatinginformation related to the synchronized stream data; analyzing thetransport stream and generating information related to the transportstream; determining whether to inject the selected synchronized streamdata based on the information related to the synchronized stream dataand the information related to the transport stream: outputting thecorresponding synchronized stream data based on the determination;re-stamping the synchronized stream data outputted with a newpresentation time stamp; and multiplexing the transport stream and thesynchronized stream data.
 44. The method as recited in claim 43, whereinthe synchronized stream data is encapsulated in a MPEG-2 transportstream form.
 45. The method as recited in claim 43, wherein the methodfurther comprises a step of establishing parameter values.
 46. Themethod as recited in claim 45, wherein the parameter values comprise:the new presentation time stamp of a first data access unit (DAU) of theselected synchronized stream data; an injection period, wherein theinjection period is a time interval for injecting the synchronizedstream data into the transport stream; and a maximum number of DAUs ofthe synchronized stream data that can be injected in one injectionperiod.
 47. The method as recited in claim 46, wherein the methodfurther comprises a step of obtaining as many DAUs as the maximum numberof the DAUs by analyzing the selected synchronized stream data based onthe parameter values.
 48. The method as recited in claim 46, wherein thestep of analyzing the transport stream further comprises a step ofperiodically analyzing the transport stream based on the parametervalues.
 49. The method as recited in claim 43, wherein the informationrelated to the synchronized stream data comprises: a presentation timestamp of a corresponding DAU; and a number of transport stream packets.50. The method as recited in claim 49, wherein the method furthercomprises a step of calculating a presentation time offset by using adifference between the new presentation time stamp of a first dataaccess unit (DAU) of the selected synchronized stream data and apresentation time stamp of a corresponding DAU generated from thesynchronized stream data analyzing unit.
 51. The method as recited inclaim 50, wherein the method further comprises a step of calculating anew presentation time stamp of DAU of the synchronized stream data byadding the presentation time offset to the presentation time stamp of acorresponding DAU.
 52. The method as recited in claim 51, wherein themethod further comprises of a step of comparing the new presentationtime stamp of DAU with the presentation time stamp of a correspondingDAU generated in the transport analyzing unit.
 53. The method as recitedin claim 52, wherein the corresponding synchronized stream data isoutputted if the new presentation time stamp of DAU is larger than thePCR in the final part of the video/audio transport stream currentlyanalyzed and smaller than the summation of the PCR increase during oneperiod and the PCR of the final part.
 54. The method as recited in claim43, wherein the information related to the transport stream is a programclock reference (PCR) of the transport stream.
 55. The method as recitedin claim 43, wherein the step of analyzing the transport stream furthercomprises a step of obtaining a PCR directly from the transport streamincluding PCR within an analyzing section, and calculating PCR foranother transport stream packet based on an output rate of the transportstream.
 56. The method as recited in claim 43, wherein the step ofanalyzing the transport stream further comprises a step of obtaining thePCR by putting a reference clock that increases as 27 MHz, wherein the27 MHz is a per-second increase of PCR of the transport stream analyzingunit.
 57. The method as recited in claim 43, wherein the step ofanalyzing the transport stream further comprises a step of obtaining thePCR by establishing a value of the reference clock with the same valueas the obtained PCR and obtaining the value of the reference clock at amoment when the PCR value is needed.
 58. The method as recited in claim43, wherein if a new presentation time stamp for a first DAU is stampedin the synchronized stream data selection/establishment unit, the stepof re-stamping comprises a step of: receiving the outputted synchronizedstream data; re-stamping the presentation time stamp of a DAU byreferring to the newly stamped presentation time stamp; and outputtingthe re-stamped presentation time stamp of the DAU.
 59. The method asrecited in claim 58, wherein the step of re-stamping further comprisesof a step of: calculating a presentation time offset value by using thedifference between the presentation time stamp of the first DAU of thesynchronized stream data and the new presentation time stamp stamped;and re-stamping the presentation time stamp of all DAUs by adding thepresentation time offset value to the presentation time stamp of allDAUs.
 60. The method as recited in claim 43, wherein the step ofmultiplexing comprises a step of injecting DAUs of the outputtedsynchronized stream data into the places of null packets in thetransport stream within a section analyzed, instead of the null packets.61. The method as recited in claim 43, wherein if a number of DAUs ofthe synchronized stream data multiplexed in the transport streamanalyzed is more than two, the step of multiplexing further comprises astep of injecting the DAUs into the transport stream in the order ofquick presentation time stamp, and the locations for DAU to be injectedinto are moved from a part where PCR of the analyzed transport stream issmall to a part where PCR of the analyzed transport stream is large. 62.An apparatus configured to inject synchronized stream data into atransport stream, the apparatus comprising: a synchronized stream dataselection/establishment unit configured to select synchronized streamdata corresponding to the transport stream; a synchronized stream dataanalyzing unit configured to analyze the selected synchronized streamdata and generate information related to the synchronized stream data; atransport stream analyzing unit configured to analyze the transportstream and generate information related to the transport stream; asynchronized stream data injection/management unit configured todetermine whether to inject the selected synchronized stream data basedon the information related to the synchronized stream data and theinformation related to the transport stream, and control the datastoring unit to output the corresponding synchronized stream data basedon the determination; and a presentation time stamp re-stamping unitconfigured to re-stamp the synchronized stream data outputted from thedata storing unit with a new presentation time stamp.
 63. A method forinjecting synchronized stream data into a transport stream, the methodcomprising: selecting synchronized stream data corresponding to thetransport stream; analyzing the selected synchronized stream data andgenerating information related to the synchronized stream data;analyzing the transport stream and generating information related to thetransport stream; determining whether to inject the selectedsynchronized stream data based on the information related to thesynchronized stream data and the information related to the transportstream; outputting the corresponding synchronized stream data based onthe determination; and re-stamping the synchronized stream dataoutputted with a new presentation time stamp.